Synchronizing mechanism in a vehicle gearbox

ABSTRACT

Synchronizing mechanism in a gearbox, preferably a vehicle gearbox, including a synchronizing muff (14) non-rotatably connected to a shaft (1) and coacting with an engagement sleeve (36) surrounding the muff (14), the sleeve being axially displaceable for meshing with teeth (11) on a first synchronizing ring rotatably mounted on the shaft (1), the ring being non-rotatably joined to a gear (6) and formed with a conical friction surface (12) for coaction with a complementary conical friction surface (22) on a second synchronizing ring (21) for synchronizing the rotation of the gear (6) and shaft (1), the periphery of the synchronizing muff (14) being formed with a number of radial recesses (17) in which radial locating abutments (23) on the second synchronizing ring (21) engage. The invention is distinguished in that each locating abutment (23) is formed with a radial hole (24) in which a detent body (25) is displaceably mounted and adapted for being brought by spring means (31,32) into coaction with an interior annular groove (37) in the engagement sleeve (36), the second synchronizing ring (21) being axially centered relative the synchronizing muff (14) by the detent bodies (25) and the spring means (31, 32). The second synchronizing ring is located by the detent bodies (25) and does not require any further fixing, which substantially simplifies the mechanism and decreases the space requirement.

The present invention relates to a synchronizing mechanism in a gearbox,preferably a vehicle gearbox, including a synchronizing muffrotationally fixed to a shaft and having external engagement teethcoacting with internal engagement teeth on an engagement sleevesurrounding the synchronizing muff, this sleeve being axiallydisplaceable for engaging engagement teeth on a first synchronizing ringrotatably mounted on the shaft and unrotatably joined to a gear andformed with a conical friction surface for coaction with a complementaryconical friction surface on a second synchronizing ring forsynchronizing the rotation of the gear and the shaft.

For the purpose of facilitating the engagement of different gears in agearbox it is usual to arrange synchronizing mechanisms ensuring duringa gear-changing operation that the gears, which are to be engaged, aregiven the same rotational velocity before engagement takes place. Suchsynchronizing mechanisms may be implemented in different ways, butusually the elements which are to be coupled together are each providedwith a conical friction surface, and by axial displacement of at leastone of the elements the friction surfaces are brought into gliding andengagement against each other such that the elements assume the samerotational velocity. In order that the synchronization shall take placesmoothly and rapidly it is desirable that the friction surfaces are madeas large as possible and at a large radial distance from the center ofrotation. To enable production of a comparatively small gearbox it ishowever also desirable to implement the synchronizing mechanism withsmall dimensions. These two contrasting desires have led to knownsynchronizing mechanisms often being compromise solutions.

The present invention relates to a synchronizing mechanism which meetsthe mentioned basic requirements with respect to the size of thefriction surfaces and their radial distance from the center of rotationwhile at the same time the implementation of the synchronizing mechanismonly requires comparatively small dimensions in axial extension.

In the inventive embodiment, a synchronizing muff is unrotatably joinedto a shaft and with engagement teeth coacts with an engagement sleevesurrounding the synchronizing muff, the sleeve being axiallydisplaceable for engaging engagement teeth on a first synchronizing ringrotatably mounted on the shaft. This ring is non-rotatably joined to agear and is formed with a conical friction surface for coaction with acomplementary conical friction surface on a second synchronizing ring,the periphery of the synchronizing muff being formed with a number ofradial recesses in which radial locating abutments on the othersynchronizing ring engage. The invention is thereby mainly characterizedin that each abutment is formed with a radial hole in which a detentbody is displaceably mounted and adapted for being brought by springmeans into coaction with an interior annular groove in the engagementsleeve, the second synchronizing ring being axially centered relativethe synchronizing muff by the detent bodies and the spring means.

Since the second synchronizing ring is located by the detent bodies itdoes not require any further attachment, which substantially simplifiesthe mechanism and reduces space requirements.

In an advantageous embodiment, the synchronizing muff is axially fixedrelative to the shaft, and as a result of the engagement of the detentbodies in the interior groove of the coupling sleeve during asynchronizing operation it is only the second synchronizing ring whichis given axial displacement to and from the engagement position with thefirst synchronizing ring. Disengagement of the detent bodies from theinterior groove in the engagement sleeve can only take place when themembers intended to be synchronized assume the same rotational velocity.The inventive implementation means that necessary force for operatingthe synchronizing mechanism will be comparatively small.

Further distinguishing features of the invention are apparent from thefollowing description of an embodiment exemplifying the invention. Thedescription will now be carried out with reference to the accompanyingdrawings, of which

FIG. 1 is an axial longitudinal section I--I of an inventivesynchronizing mechanism in a vehicle gearbox, and

FIG. 2 is an axial cross section II--II of the mechanism illustrated inFIG. 1.

In the embodiment illustrated in FIG. 1, a gear hub 3 is rotatablymounted on a shaft 1 with the aid of a needle bearing 33, the gear hubbeing axially fixed to the shaft 1 with the aid of a locking ring 4.With the aid of splines 5, the hub 3 is non-rotatably connected to agear 6 and an outer synchronizing ring 7. These contact each otheraxially and are axially fixed in position on the hub 3 by two lockingrings 8,9. The gear 6 is conventionally disposed for coaction with othergears (not shown) in the gearbox to form different gear ratios. Theouter synchronizing ring 7 is formed with exterior engagement teeth 11and on its side facing away from the gear 6 it is formed with aninterior conical friction surface 12.

A synchronizing hub 2 is conventional attached to the shaft 1, and thishub is mountably connected with the aid of splines 13 to a synchronizingmuff 14 surrounding the hub 2. The muff 14 is axially fixed between twolocking rings 15,16 on the synchronizing hub 2. The synchronizing muff14 is provided in its periphery with four radial recesses 17 at uniformangular spacing. One such recess 17 is illustrated in FIG. 2, from whichit will be seen that the recesses 17 are open radially outwards and withpurely radial side surfaces 18 merge radially inwards into two inwardlysloping surfaces 19 to a somewhat narrower bottom recess 20.

An inner synchronizing ring 21 is arranged between the synchronizingmuff 14 and the outer synchronising ring 7 in an axial direction. Thisring is formed with an exterior conical friction surface 22 intended forcoaction with the friction surface 12 on the outer synchronizing ring 7.The inner synchronizing ring 21 is formed with four axial locatingabutments 23, which axially thrust into the respective recess 17 in thesynchronizing muff 14. The abutments 23 have a radial extension and areprovided with radial holes 24. A detent body 25 is displaceably mountedin each of these holes 24.

Each detent body 25 is radially inwardly formed with a bottom plate 26fitting into the respective bottom recess 20. This plate 26 is formedwith sloping side surfaces 27 having substantially the same slope as theinner sloping faces 19 of the recesses 17. Axially, the bottom plates 26are formed with straight sides and constitute spring seatings 28extending axially outside the recess 17 on either side of thesynchronizing muff 14. Radially inwards these spring seatings 28 areformed with weakly inwardly sloping engagement surfaces 29, the slope abeing preferably about 5° relative a centerline 30 of the shaft 1. Theslope a is directed such that the radii of the engagement surfaces 29decrease with increased axial distance from the recess 17. Two annularsprings 31,32, one on either side of the synchronizing muff 14 and bothbeing common to all the detent bodies 25, engage against the engagementsurfaces 29 of the spring seatings 28.

The annular springs 31,32 act on the detent bodies 25 with radiallyoutwardly directed forces. Above the bottom plates 26, the detent bodies25 are substantially cylindrical, but their radially outward parts arebevelled in an axial direction for coaction with an engagement sleeve36.

The synchronizing muff 14 is formed with exterior axial engagement teeth34 for meshing with internal engagement teeth 35 on the engagementsleeve 36 surrounding the synchronizing muff 14. In an axially centralposition, the engagement sleeve 36 is provided with an interior annulargroove 37 having a cross section shaped like a trapezium with twoparallel sides. The outer portions of the detent bodies 25 are adaptedfor engagement in this groove 27 when the engagement sleeve 36 assumes adisengaged position corresponding to that in FIG. 1. The engagementsleeve 36 is outwardly formed with an annular groove 38 for coactionwith an unillustrated gear-change fork conventionally displacing theengagement sleeve 36 axially.

As previously mentioned, FIG. 1 illustrates the synchronizing mechanismin a disengaged condition. It is here assumed that the shaft 1 and thesynchronizing muff 14 rigidly connected to it rotate at a given highspeed, while the gear 6 and the outer synchronizing ring 7 rigidlyattached to it are assumed to rotate at a low speed. An engagementsequence is initiated by the engagement sleeve 36 being moved towardsthe gear 6, i.e. to the left in FIG. 1. With the aid of its internalgroove 37 the engagement sleeve 36 will thus cause the detent bodies 25to accompany it and displace them, thereby also the inner synchronizingring 21 until the latter is pressed into engagement against the outersynchronizing ring 7. Since the synchronizing rings 7 and 21 rotate atdifferent velocities, sliding will occur between the friction surfaces12 and 22, which successively evens out the difference in velocitypresent. During the evening-out phase, a relative angular motion betweenthe inner synchronizing ring 7 and the synchronizing muff 14 isobtained, resulting in that the locating abutments 23 of the innersynchronizing ring 21 are urged against the side surfaces 18 of therecesses 17.

The engagement sleeve 36 is here prevented from being displaced furtherby the detent bodies 25 engaging against the side surfaces 18 of therecesses 17 and the inwardly sloping edge surfaces 19 in thesynchronizing muff 14, thereby preventing the detent bodies 25 frombeing displaced into the bottom recesses 20 of the recesses 17. Onlywhen the velocities of the synchronizing rings 7,21 have been evened-outis it possible to urge with normal force the detent bodies 25 into thebottom recesses 20, and thereby disengage the engagement sleeve 36. Thismay then be further displaced axially so that its engagement teeth 35can be meshed with the engagement teeth 11 on the outer synchronizingring 7, while meshing with the engagement teeth 34 of the synchronizingmuff 14 is retained. In this condition the gear 6 is thus non-rotatablyengaged with the shaft 1.

At the same time as the detent bodies 25 and the inner synchronizingring 21 are moved to the left in FIG. 1, the right-hand annular spring32 is brought into engagement with the synchronizing muff 14 and itsfurther displacement is inhibited. At continued axial displacement ofthe detent bodies 25, the bottom plate 28 formed as a spring seatingwill glide relative the spring 32 which, as a result of the conical formof the engagement surface 29, results in a further tensioning of thespring 32. The bottom plates 26, and thus the inner synchronizing ring21 also, will therefore be acted on by an equalizing force striving toaxially center the synchronizing ring 21 relative the synchronizing muff14. This is advantageous when the synchronizing mechanism is in adisengaged state, since it ensures that the friction surfaces 12,22 ofthe synchronizing rings 7,21 do not engage against each other and thuscause friction losses. At the same time, it is also possible to reducethe necessary play between the friction surfaces 12,22 in a disengagedstate, which means that the synchronizing mechanism can be given acorrespondingly shorter implementation.

Within the scope of the following claims, the invention may be modifiedand formed differently than has been exemplified in the abovedescription. Accordingly, synchronizing means can to advantage bearranged on both sides of a common synchronizing muff 14, i.e. a furthergear can be arranged to the right of the muff 14 in FIG. 1.

In such a case, the synchronizing muff 14 is formed with furtherrecesses to which abutments from a synchronizing ring are adapted in acorresponding manner to what has been described above. Annular springs31,32, synchronizing muff 14 and connection sleeve 36 are thus commonfor both synchronizing means, which decreases the space requirement andpermits small dimensions in such gearboxes.

I claim:
 1. A synchronizing mechanism in a gearbox, preferably a vehiclegearbox, including a synchronizing muff (14) rotationally fixed to ashaft (1) and having external engagement teeth (34) coacting withinternal engagement teeth (35) on an engagement sleeve (36) surroundingthe synchronizing muff (14), this sleeve being axially displaceable forengaging engagement teeth (11) on a first synchronizing ring (7)rotatably mounted on the shaft (1) and unrotatably joined to a gear (6)and formed with a conical friction surface (12) for coaction with acomplementary conical friction surface (22) on a second synchronizingring (21) for synchronizing the rotation of the gear (6) and the shaft(1), the periphery of the synchronizing muff (14) being formed with anumber of radial recesses (17) in which radial locating abutments (23)on the second synchronizing ring (21) engage, characterized in that eachabutment is formed with a radial hole (24) in which a detent body (25)is displaceably mounted and adapted for being brought by spring means(31,32) into coaction with an interior annular groove (37) in theengagement sleeve (36), the second synchronizing ring (21) being axiallycentered relative the synchronizing muff (14) by the detent bodies andthe spring means (31,32).
 2. A synchronizing mechanism as claimed inclaim 1, characterized in that each detent body (25) is formed with abottom plate (26) axially formed with bevelled end planes (27) and in atransverse direction acting as spring seatings (28) for the spring means(31,32) acting against the detent body (25).
 3. A synchronizingmechanism as claimed in claim 2, characterized in that the spring means(31,32) are two annular springs, located axially on either side of thedetent bodies (25) urging them radially outwards.
 4. A synchronizingmechanism as claimed in claim 3, characterized in that the bottom plates(26) formed as spring seatings on the detent bodies (25) are formed withengagement surfaces (29), for the spring means (31,32), that areundercut relative the respective center lines of the detent bodies (25).5. A synchronizing mechanism as claimed in claim 1, characterized inthat each recess (17) in the synchronizing muff (14) is formed withradially directed side surfaces (18) which, by inwardly sloping edgesurfaces (19), merge into a centrally situated narrower bottom recess(20) in which the detent body (25) can be accommodated on disengagementfrom the engagement sleeve (36).
 6. A synchronizing mechanism as claimedin claim 5, characterized in that in the engaged state for the detentbodies (25) in the engagement sleeve (36), each recess (17) allowsturning of the synchronizing muff (14) relative the second synchronizingring (21), said turning being limited by the locating abutments (23) onthe second synchronizing ring (21) pressing against the edge surfaces(18,19) in the recesses (17), thereby locking the detent bodies (25) insaid state of engagement.